Human blood consists of
(i) Red Blood Corpuscles (R.B.C.) or Erythrocytes
(ii) White Blood Corpuscles (Leukocytes, W.B.C.)
(!!!) Thrombocytes and
They are circular, bi-convex disc-like in shape and can be seen under a microscope. Pale yellow in colour, they contain haemoglobin, a compound of iron. They give the blood its typical colour due to their preponderance, their ratio being 500:1 for (RBC: W.B.C.) respectively. The haemoglobin present in RBCs reacts with pure oxygen to form oxy-haemoglobin, which is carried to different body parts for oxygen supply.
White Blood Corpuscles are very few and have no definite shape. Their movements are like those of an Amoeba. Also called leucocytes, they act like soldiers of the body and protect it from microbial attacks. Plasma is a pale yellow liquid and contains 90% water. The corpuscles float in this medium.
CLOTTING OF BLOOD
Plasma consists of fibrinogen and serum. In the event of an external cut or injury on the body, fibrinogen is converted into fibrin which, being insoluble in serum, forms a network, in the meshes of which, blood corpuscles get trapped. It leads to the formation of a blood clot, which stops further bleeding, thereby helping the body conserve this crucial resource. Some people, due to a hereditray defect, do not experience the clotting of blood in case of injury. This medical condition is known as haemophilia.
(a) It supplies oxygen to various organs of the body.
(b) It removes nitrogenous waste products of the body.
(c) It supplies digested food to various organs of the body.
(d) It defends the body against the attack of germs.
(e) It carries the secretions of ductless glands (hormones) to different organs.
(f) It helps maintains a constant internal temperature inside the body, which is crucial to normal physiological working of the body.
It refers to the introduction of the blood with a similar composition and nature into a person suffering from a deficit of blood. It is absolutely safe to donate 250 c.c. or 8% of blood volume at a time if the blood groups have been properly matched. Blood Banks are there in all big cities where people can donate blood, which is stored at low temperatures and used later. These days, it is possible to segregate different components of blood and use them separately for different patients as per their specific needs. This process avoids any kind of wastage of blood components.
Karl Landsteiner (1901) is credited with the idea of classification of blood. This idea is based on the concept of antigen-antibody reactions. His classification of blood groups is : AB, A, B, and O. Patients must be given a blood transfusion of their own group with the exception of Group O, which is a universal blood group (Can donate blood to any other blood group). A person with blood group AB, as per this system, is the universal recipient i.e. can receive blood of any other blood group.
Another popular classification of blood groups is based on the presence or absence of a chemical factor known as Rh factor (derived from Rhesus monkey). If a person has the Rh factor in his blood, he is referred to as Rh+ while an Rh - person does not have such a factor in his blood. This is an aspect to be considered while transfusing blood because mixing Rh+ with Rh – blood leads to agglutination (clumping together) and immediate death.